Electrophotographic process using polyamide containing developer

ABSTRACT

A developer mix for use in electrostatic printing to develop latent images, including charged and uncharged areas of an image bearing sheet said developer mix comprising separate granular carrier particles, and a developer powder comprising a coloring agent and a resin having a triboelectric relationship of opposite polarity with respect to said carrier granules, said resin comprising a blend of resins in which the physical properties of the blend are distinct with respect to the physical properties of the resin components which are heat blended together, the principal resin being a polyamide resin which represents the infrangible resin component, and the completed resin being reduced to a melt point within the range of 8*, whereby developed images of substantially improved black density may be formed over extended operating periods.

[111 3,901,695 1451 Aug. 26, 1975 1 1 ELECTROPHOTOGRAPHIC PROCESS USINGPOLYAMIDE CONTAINING DEVELOPER [75] Inventor: Loren E. Shelffo,Palatine, Ill.

[73] Assignee: Addressograph Multigraph Corporation, Cleveland, Ohio[22] Filed: May 21, 1973 [21] Appl. No.: 362,410

Related US. Application Data [60] Division of Ser. No. 123,065, March10, 1971, Pat. No. 3,764,538, which is a continuation of Scr. Nov692,732, Dec. 22, 1967, abandoned, which is a continuation-in-part ofSer. No. 357,743, April 6, 1964, abandoned.

3,565,654 2/1971 Story 252/621 3,650,797 3/1972 Tomanek 3,764,53810/1973 Shelffo 252/62.l

OTHER PUBLICATIONS T875,005, Tower Composition for DevelopingElectrostatic Images, Beyee et al., 875 0.6. 12.

Primary ExaminerRoland E. Martin, Jr.

[5 7 ABSTRACT A developer mix for use in electrostatic printing todevelop latent images, including charged and uncharged areas of an imagebearing sheet said developer mix comprising separate granular carrierparticles, and a developer powder comprising a coloring agent and aresin having a triboelectric relationship of opposite polarity withrespect to said carrier granules, said resin comprising a blend ofresins in which the physical properties of the blend are distinct withrespect to the physical properties of the resin components which areheat blended together, the principal resin being a polyamide resin whichrepresents the infrangible resin component, and the completed resinbeing reduced to a melt point within the range of 8, whereby developedimages of substantially improved black density may be formed overextended operating periods.

16 Claims, No Drawings lELlEE'lflROlllllOTOGR/XPHIC PROCESS USINGllUlLlKll/illllllll CONTAINING DEVELOPE CROSS-REFERENCE TO RELATEDAPPLICATIONS This application is a division of my copending applicationSer. No. 123,065, filed Mar. I0, 1971, now U.S. Pat. No. Ser. 3,764,538,which is a continuation of copending application SEr. No. 692,732, filedDec. 22. 1967, now abandoned, which in turn is a continuationin-part ofprior copending application Ser. No. 357,743, filed Apr. 6, 1964, nowabandoned all assigned to the same assignee as the instant application.

This invention relates to electroscopic powders of the type useful inrendering visible the latent electrostatic images produced byphotoelectrostatic or electrostatic copying. More particularly itrelates to improved electroseopic powders for use in automated typephotoelectrostatic copying apparatus.

in photoelectrostatic copying processes, an electrostatic charge patternis created on a charge photoconductive layer, such as zinc oxide orselenium, by exposure to a light pattern. Various techniques and deviceshave been employed to expose the charged surface, such as projection orcontact printing methods, fiber optic imaging devices, and variousphosphor display devices. Upon exposure of the charged layer to lightunder darkroom conditions, a latent electrostatic charge image isformed.

Still other image generating devices are employed that directly deposita charge pattern corresponding to the graphic subject matter by the useof single or multiple styli. The technique of direct imaging may becarried out in the presence of light.

Irrespective of the technique employed for creating a latentelectrostatic charge image, it must be rendered visible by developmentwith a suitable resinous, thermoplastic, electroscopic powder andrendered permanent by the application of heat, pressure, solvent vaporor other fixing technique. The developed image may be fixed in place onthe surface upon which it is formed, or it may be transferred to a newsurface and fixed thereon.

A number of techniques are available and in wide use for carrying outthe developing step which brings the electroscopic powder, or tonerpowder as it is known in the art, into contact with said latent image.These include, for example, powder cascade, powder cloud, and drymagnetic brush development. The advancement represented by the improvedelectroscopic powders of this invention is applicable to all of theforegoing systems where a charge-sensing powder is brought into contactwith an clectrostatically charged surface for the purpose of producing avisible image.

Further discussion of the improvements represented by this inventionwill be explained in terms of the magnetic brush type of apparatus, butthe novel electroscopie powders disclosed herein can also be used withequal advantage in other developing apparatus and their use is notlimited to magnetic brush techniques.

The magnetic brush method for developing an electrostatic image involvesthe use of a mixture of magnetically attractable particles andclectroscopic powder. This mixture or developer mix" is formed up into abrush-like mass on the surface of a cylindrical roll under the influenceofa magnetic field created by magnetic means disposed within said roll.

The electroscopic powder is held to the magnetically attractable carrierparticles by a triboelectric effect whichresults from frictional contactbetween the particles. This effect is more fully described in U.S. Pat.No. 2,874,063 dated Feb. 17, 1959. The relative position in thetriboelectric series of carrier and electroscopic powder materials willdetermine the polarity of the charge generated on the electroscopicpowder. Hence, particular materials can be selected for either positiveor reversal printing. In practice, the electroscopic powders are mixedwith larger carrier particles, such as iron, ferrites, magnetites,cobalt, and nickel. The car'- rier particles align themselves along thelines of magnetic flux provided by the magnetic means so that they standerect on the surface of the cylinder. In this manner the particles,carrying the electroscopic powder present a uniform and continuous arrayof developer mix along that portion of the roll which contacts theelectrostatic recording member bearing the latent electrostatic imagethereon.

U.S. Pat. No. 3,003,462 discloses a typical magnetic brush developmentapparatus wherein the developer mix is deposited in a trough, thereafteris picked up on the periphery of an applicating cylinder having themagnetic means therein, and is formed into a brush in the environment ofsaid magnetic field. As the rotating applicator cylinder carries thedeveloper mix outside the magnetic field, the magnetic brush collapsesand developer mix falls back into the reservoir. This cycle of brushformation and collapse is repeated as long as the developer rollrotates.

Electroscopic powders available heretofore have left much to be desiredwhen used in automated electrostatic copying machines, particularlywhere the magnetic brush-type apparatus is employed. One of the majorproblems is that of deterioration of the electroscopic powder componentof the developer mix. One evidence of such deterioration appears in thephotoelectrostatic copies which begin to show adherence of theelectroscopic powder indiscriminately in both image and non-image areas.

Another evidence of mix deterioration is a fall-off or loss in copydensity, that is, the developed image appears gray rather than having anintense black color.

Also, carrier particles may begin to deposit on the copy sheet as aresult of mix deterioration giving the photoelectrostatic copy a grittyfeel.

Still further problems caused by mix deterioration relate to impropermixing and impairment of the mechanical mixing means of the developerapparatus.

The automated photoelectrostatic office copying equipment underdiscussion is designed especially for high production, high qualitycopying. Equipment of this type is required to produce up to 6000 copiesin a typical work day. The deteriorated condition referred to above cantake place rapidly. Deterioration of known developer mixes hasheretofore necessitated complete and frequent replacement with freshmaterial.

Deterioration is caused by physical changes in the electroscopic powder.These physical changes primarily concern the particle size of thepowder. The first such change relates to particle size fracture or comminution, and the second relates to agglomeration or clumping of smallparticles into larger ones.

The forces which operate in the magnetic brush developer exert agrinding or milling action on the developer mix. Electroscopic powderparticles may be split or fractured so that the new fragments do nothave the same electroscopic properties as the particles from which theywere formed. Each of these fragments is present as a spurious particlewhich serves only to impair the performance of the developer system.

Further attrition of the particulate matter generates excessively smallparticles referred to as dust or fines that are incapable ofdiscriminating between the charged and uncharged areas. These fines tendto become airborne and create an undesirable condition from ahousekeeping standpoint.

Agglomeration or clumping is caused by an increase in mix temperature.This temperature rise may be due to the absorption by the powder offrictional energy developed through impact between the particles as theyare mixed and churned within the developer unit. Another source of heatis the high temperature fusing unit within the apparatus. Thethermoplastic toner particles begin to clump or agglomerate as theyreach their softening or tackifying temperature. In a severe conditionthe agglomerates may occlude some of the iron carrier particles. Theseclumps, containing both iron and softened electroscopic powder,completely disrupt the developing step.

These clumps often become deposited in clearances between moving andstationary mechanical parts thereby increasing the power required todrive the magnetic brush roller. The additional power is dissipated asheat so that the process of agglomeration becomes progressively worse.

Generation of the triboelectric charge on the electroscopic powderdepends upon proper contact between toner and carrier particles.Clumping and agglomeration prevent the proper circulation and blendingof toner with the carrier in the developer apparatus. A free-flowingcondition is particularly necessary during replenishment when freshtoner is added to a depleted mix. Poor circulation gives rise to anon-uniform powder mixture which produces copies that are unevenlydeveloped. Poor blending of electroscopic powder and iron particlesreduces the level of triboelectric charge generated on the powder.

The demands placed on electroscopic powders suitable for high speed,continuous automatic electrostatic copying, are exacting and haveheretofore not been met. From the foregoing discussion, it is seen thatthe thermoplastic, resinous toner particle must have certain distinctproperties if it is to achieve a practical mix life in a magnetic brushdeveloping apparatus.

The resin blend should be sharp-melting so that it is converted fromdiscrete, solid pieces to a flowable material over a temperature rangenot greater than about 5 to 8F. Such a resin blend will flow smoothlyonto the paper to form a permanent image and solidify rapidly whenremoved from the fuser, thus producing an image which will not smear.The thermoplastic resin should remain in a solid state at temperaturessubstantially higher than room temperature so that it does not soften,become tacky, and form cakes, clumps, or agglomerates. Such a divergenceof requirements demands that the thermoplastic resin be at once toughand resilient enough to withstand the grinding action in the developerapparatus, yet sufficiently brittle and frangible to permit itsreduction to powder on conventional grinding equipment.

Some thermoplastic compositions. which are tough and infrangible, haveexcellent clectroscopic properties, but cannot be manufactured onconventional milling equipment. Other resins which may have excellentelectroscopic properties and which may be readily ground to a desiredparticle size in conventional milling equipment are too brittle orfrangible for the magnetic brush apparatus. These are reduced to aninordinate amount ofdust and fines by the mixing action of the developerunit.

It is a primary object of this invention to provide an electroscopicpowder particularly suitable for use in automated and continuousphotoelectrostatic copying machines.

It is an object of this invention to provide an electroscopic developingpowder having greatly improved resistance to deterioration in magneticbrush developer apparatus.

It is a further object of this invention to provide an electroscopicdeveloping powder that will fuse in a narrow temperature range below thechar point of paper and will resist clumping or agglomeration.

It is a further object of this invention to provide electroscopicdeveloping powder which is resistant to attrition or grinding when usedin'a magnetic brush developer apparatus.

It is a still further object of this invention to provide anelectroscopic developing powder comprised of a blend of thermoplasticresins having suitable frangibil ity properties and temperature responsecharacteristics that will produce consistently high qualityelectrostatic copies having a high contrast between image and nonimageareas.

These and other objects are apparent from and are achieved in accordancewith the following disclosure.

The electroscopic powders which constitute this invention comprise ablend of a tough, infrangible synthetic resin with a highly frangiblethermoplastic synthetic resin which melts between about C. 158F.) and165C. (329F.), preferably in the range of 213-235F., said blend havingthe critical property of going from discrete particles to flowablematerial in a range from 508F. The blend of synthetic thermoplasticresin materials preferably should have a correspondingly high softeningpoint, that is, the thermoplastic particles should remain discrete attemperatures up to F. and not adhere to one another or formagglomerates. The preferred average particle size of the electroscopicpower ranges from 4 to 10 microns with the over-all range of particlesizes ranging from 1 micron to 74 microns.

The invention is directed to a novel thermoplastic resinouselectroscopic powder comprising a tough, infrangible resin component,such as a thermoplastic polyamide resin, which is chemically blendedwith a highly frangible, brittle substance such as a rosinmodifiedmaleic anhydride-polyhydric alcohol resin, an unsaturated co-ester resinsuch as a diphenol resin esterified with a fatty acid, or a purenon-heat reactive phenolic resin.

The powder blends may optionally include additives such as polyolresins, toluenesulfonamides, or butylated-hydroxy-toluene which enterinto the blends as fluxing agents, tending to decrease the meltviscosity of the thermoplastic blend.

The preferred polyamide resins are produced by the reaction of highmolecular weight polyene fatty acids and their esters with an amine. Byreacting ammonia. a primary or secondary amine, a hydroxyamine or analkanolamine, with a high molecular weight carboxylic acid or an esterthereof, either saturated or unsaturated, said acid or ester beingobtainable by polymerizing at elevated temperature said polyene fattyacid or esters thereof. and in the case of the esters, converting thepolymers to the corresponding acid if desired, there are produced thepreferred polyamides. Examples of polyene fatty acids in esterified formare 9,11- and/or 9,12octadecadienoic acid (obtainable from soybean oiland dehydrated castor oil), linoleic acid, alpha and beta-eleostearicacid (obtainable from tung oil). The preferred esters are those derivedfrom methanol, ethanol, and propanol. Primary or secondary amines may beused such as, for example, methylamine,ethylamine, propylamine,ethylenediamine, tetraamethylenediamine, pentamethylenediamine,piperazine, and diethylenetriamine. The class of thermoplastic,polyamide resins is disclosed in U.S. Pat. No. 2,379,413 and sold by theGeneral Mills Company under the trademarks Versamide" and Omamid". Othersuitable polyamide resins are also available from the Krumbhaar ResinDivision of Lawter Chemicals, Inc., under the trademark Polymid.

The second thermoplastic constituent in the electroscopic powder isextremely frangible but it is sharp melting. A suitable frangibleconstituent may be a rosin-modified phenolic resin, such as thoseprepared by modifying a phenol formaldehyde resin with the reactionproduct of maleic anhydride and rosin or a polyhydric alcohol such asglycerol or pentaerythrytol. Such rosin-modified phenolic resins aresold under the trademark Amberol" by Rohm & Haas Company. Diphenolicresin materials esterified with a soya fatty acid and certainthermoplastic phenolformaldehyde resins exhibit satisfactory frangibleproperties. The esterified diphenolics are available from the JohnsonWax Company Chemical Division of Racine, Wis, and the thermoplasticphenol-formaldehyde resins are available from the Krumbhaar ResinDivision of Lawter Chemicals. Inc., and from Nelio Chemicals, Inc.,Jacksonville, Fla.. as their VBR-800 series resins.

The blend ofinfrangible and frangible resins with coloring materialsforming the electroscopic powder should be highly infrangible and shouldhave a fracturing value of at least 400 gram-centimeters when measuredon a wafer of resin 3.75 cm, in diameter and 0.5 cm. in thickness at100F. by the falling ball method. In this method, as adapted fromAmerican Institute of Mining and Metallurgical Engineers, Vol. 87, p.35. 1930, the resin wafer is subjected to impact by a falling ball andthe energy (measured in gram-centimeters) required to just fracture thewafer is measured. The infrangible resin component of the resin blendshould preferably have a fracturing value of at least 1000gramcentimeters in the foregoing test while the frangible resincomponent may have low fracturing values in the range of 100-200gram-centimeters.

The resin blend forming the electroscopic powder should not soften orbecome tacky at temperatures below 130F. The softening properties ofresins can be measured with a penetrometer by the procedure of A.S.T.M.Standard No. D5-61. By this procedure. it has been found that resinblends which permit a maxis a it having molecular weights in the rangefrom 1000 to 2000. Purified wood resins such as those sold by HerculesPowder Company under the name M-Wood Rosins, and toluenesulfonamidesavailable under the trademark Santicizer 8 and Santicizer 9 fromMonsanto Chemical Company are also suitable.

The various thermoplastic resins are compounded by reducing the resinousmaterials to the molten state and then blending in the requiredpigments, dyes, and coloring agents and the fluxing materials where theyare to be included, using conventional mixing equipment.

FORMULATION NO. 1 (Major percentage of tough. infrangible resin)Polyamide Resin -907: Frangible resin component (phenolic maleicanhydridepolyhydric alcohol resin 5-407: Polyols 0-1071 Nubian resinblack 1-571 Carbon black pigment (Nee-spectra. Mark III) 1-571FORMULATION NO. 2 (Minor percentage of tough. infrangible resin)Polyamide Resin 9-507L Frangible resin component (Pure phenolicsKrumbhaar K254 50-90% Polyols 0-1071 Nubian resin black 1-671 Carbonblack pigment (Ned-spectra. Mark 11]) 1-271 The following examples aregiven to illustrate preferred embodiments and process for producingelectroscopic powders embodying this invention. It will be understoodthat this invention is not limited to these examples.

In these examples, all percentages are given on a weight basis.

EXAMPLE 1 Electroscopic powder formulation is: Synthetic. polyamide.thermoplastic resin (Versamide 930) Polyol (Shell X-450) Maleicanhydride-polyhydric alcohol rosin-modified resin (Amherol X00. Rohm &Haas -Continued Company) 49.5% Nubian resin hluck dye 6.6 7: Carbonblack pigment (Nco-spectru, Mark 11) 1.07:

The quantity of polyamide resin called for is heated in a suitablevessel equipped with a conventional impeller type mixer until the resinis just molten so that it can be stirred. To the molten polyamide resinis added the Polyol while the mass is being agitated. Agitationcontinues during the addition of the maleic anhydridepolyhydric alcoholresin-modified resin. After the maleic anhydride-polyhydric alcoholresin is completely melted, the quantity of black dye is added to thebatch followed by the addition of the carbon black.

After the batch has been thoroughly mixed, it is removed from the mixingvessel, cooled, crushed and pulverized to an average particle sizeranging from 4-10 microns. Understandably there will be particle sizesranging from under one micron to 50 microns and larger. As a final step,the electroscopic powder is passed through a 200 mesh screen so that thelargest particle size possible in such an electroscopic powder would beunder 75 microns.

The softening point of the electroscopic powder was measured by placinga quantity of the electroscopic powders in a constant temperature ovenfor 12 hours. A series of oven tests, at different temperature levels,revealed that powder produced in Example I remained in particulate form,and did not clump or agglomerate until tested at a 155F. level. The meltpoint of the electroscopic powder was in the range of 215220F. measuredin accordance with A.S.T.M. Method No. E2- 8-58T.

The image copies were of uniform density indicating complete andthorough mixing between the carrier and powder. A high image density wasmaintained throughout the run while non-image areas remainedclean andfree of spurious toner deposition A copy is considered to have properimage density if reflectance density measurements, taken by a standardPhotovoltmeter, are above 1.0 units.

Similarly, reflectance readings can give a measure of the contrastbetween the image and non-image areas. The non-image area on a processedcopy should not measure more than 0.05 Photovolt units. The copies wereclean in the non-image areas giving Photovolt reading less than 0.05units.

The copies were not gritty" indicating that the carrier particles werebeing retained in the system and not occluding on the powder.

EXAMPLE 2 ingredients: Polyumide resin (Versumide 930) 749! Mulcicanhydridc-polyhydric alcohol rosin-modified resin (Amhcrol 800) I991Nubian resin black dye 5.6% Carbon hluck pigment (Nee-spectra. Mark ll)1.4%

The ingredients were processed in accordance with the steps set forthfor Exammle 1 above. The melting point range and softening point of theabove electroscopic powder were 2l3-220F. and greater than 140F.,respectively. lt will be noted that this example incorporates a majorpercentage of the tough, infrangible polyamide material. Photovoltreadings were all above 1.0 units. Such an electroscopic formulationfinds particular utility in environments where the copying equipment isused for extended periods of time and where there is a high ambienttemperature.

EXAMPLE 3 An electroscopic powder was prepared in accordance with theprocedure of Example 1 wherein the electroscopic powder was comprisedlargely of polyamide material.

Ingredients:

Polyamide resin (Versamide 930) Maleic anhydride-polyhydric alcoholrosin-modified resin (Amberol 800) 7'7: Nigrosine dye 6'71 Polyols 8%Carbon black pigment (Neo-spectra. Mark II) 1'72 The melting point rangeand the softening point of the granular mass were 2l7222F. and greaterthan F., respectively. The formulation of Example 3 is suitable for useunder high temperature conditions. The inclusion ofa fluxing agent tendsto lower the melt point slightly and give a more uniform image.

EXAMPLE 4 Ingredients: Polyamide resin (Versamide 930) 3371 Polyol(Shell X-450) fluxing agent 9.971

Phenolic Resin (No. K-254 Krumbhaar Chem. Div. of

Lawter Chemicals. Inc.) 49.57: Nubian resin black (National Aniline)6.671 Carbon black pigment (Nco-spectra. Mark ll) 19;

The above formula has substituted for the maleic anhydriderosin-modified resin a pheno-formaldehyde resin which is a highlyfrangible. sharp melting thermoplastic material. The performance of thisformulation in respect of print quality and resistance to developer mixdeterioration was fully equivalent to that observed in Example 1. Themelting point range and softening point of the above example were2l5220F. and greater than 140F., respectively.

EXAMPLE 5 EXAMPLE 6 The electroscopic powder prepared in this exampleconformed to the formula set forth in Example 1 above with the exceptionthat a mixture of orthoand para-N- ethyl-toluenesulfonamides (Santicizer8, Monsanto Chemical Company) was substituted as a fluxing agent for thepolyol (Shell X-450), The copy quality obtained was fully equivalent tothe copy quality obtained from the formulation of Example 1.

EXAMPLE 7 This example'differs from Example 1 chiefly in the use oflesser percentages of polyamide resin blended with the highly frangiblethermoplastic material. It has been found that the addition of polyamidein amounts less than 9% by weight in the electroscopic powder formulahas little or no effect on improving its resistance to the grinding andmilling action present in the developer apparatus.

Polyamicle resin (Versamide 930) 97? Maleic anhydride-polyhydric alcoholrosin'modified resin (Amberol 800) 83.2% Nubian resin black 6% Carbonblack (Neo-spectra, Mark ll) 171 The above composition had a meltingpoint range and softening point of 220-228F. and above l55F.,respectively. Electroscopic powders formulated with 5-6% polyamidedeteriorated after 3,0005,000 electrostatic prints. improvements beginto show when the level of 9%, and above, of the polyamide thermoplasticsynthetic resin is included in the formula.

All of the foregoing examples when used in a magnetic brush developer ofthe type described in US. Pat. No. 3,003,462 gave consistently denseuniform images. The first copy from a batch of developer mix, and thelater copies made after 100 hours of continual use, pro duced printshaving a print density greater than 1.0 Photovolt readings. Reflectancein the non-image area on the developed copy of photoelectrostatic paperwas less than 0.05 Photovolt units.

With the developer mix of this invention, the formation of clouds ofdeveloper powder or throwout, in the vicinity of the developer mix, isgreatly minimized, if not completely prevented. Hence, the areas wheresuch machines are located are kept substantially clean.

A further advantage of the electroscopic powder of this invention isthat it does not agglomerate or cake during storage, and thereforeremains uniform, ready for use. It is not uncommon for materials inshipment to be exposed to a wide variety of climatic conditions,including extremely high temperatures, which often cause the powder toactually "cake" into a solid mass in the-shpping container. The materialof this invention has been found to retain its free-flowing granularconsistency, making it ready for use immediately by the operator.

The discussion of the electroscopic powder has been limited to thetechnique of positive printing wherein the triboelectric relationship ofthe electroscopic powder to the iron carriers particles is such that theparticles acquire the necessary positive charge so that they will adhereto the negatively charged electrostatic image on the photoconductivemember. The advantages provided by the electroscopic powders of thisinvention may be applied with equal success to the technique of reversalprinting as described in co-pending application Ser. No. 221,888 andassigned to the same assignee.

The present invention has been described in great detail, havingpresented the best mode of formulating the electroscopic powders. Otheruseful materials and formulations will occur to one skilled in the artover the particular embodiments described herein which are exemplary andnot intended to limit the invention, but are intended to cover theinvention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. The method of making an electrostatic copy on an electrostaticrecording member comprising the steps of electrostatically charging saidmember in the dark, exposing the charged member to a light pattern toproduce thereon an electrostatic charge image, developing said chargeimage by applying thereon an electroscopic powder, said electroscopicpowder comprising a blend of infrangible, sharp-melting, thermoplasticpolyamide resins and a sharp-melting highly frangible, thermoplasticresin, said blend being accomplished by melting the resin componentstogether to form a miscible mixture, said infrangible resin componenthaving a fracturing value of at least 1000 gram centimeters whenmeasured by the falling ball method at 100 F. on a wafer of resin 3.75centimeters in diameter and 0.5 centimeters in thickness, a meltingrange not greater than 8 F. being present in an amount ranging from 9 toby weight of said granular powder, said highly frangible resin having afracturing value not greater than 200 gram centimeters when measured bysaid falling ball method and a melting range not greater than 8 F. andthereafter fixing said developed charge image to form a permanent imageon said recording member.

2. The method of making an electrostatic copy on an electrostaticrecording member comprising the steps of:

electrostatically charging said member in the dark;

exposing the charged member to a pattern of light and shadow to producethereon an electrostatic charge image;

developing said charge image by applying thereon an electroscopic powdercomprising a resin blend of:

i. at least 9% by weight of said powder of an infrangible thermoplasticpolyamide resin formed by reacting a high molecular weight polyene fattyacid or ester thereof with an amine, said polyamide resin having afracturing value of at least 1,000 gram centimeters, and

ii. a highly frangible thermoplastic resin having a fracturing value notgreater than 200 gram centimeters,

said resin blend being formed by mixing the resin components in theirmolten state and said blend further having a sharp melting point withinthe range of about 150 F. to about 329 F., said fracturing values beingmeasured by the falling ball method on a wafer of resin maintained atabout 100 F. and 3.75 cm. in diameter and 0.5 cm. in thickness.

3. The method of making an electrostatic copy on an electrostaticrecording member comprising the steps of:

electrostatically charging said member in the dark;

exposing the charged member to a pattern of light and shadow to producethereon an electrostatic charge image;

developing said charge image by applying thereon a developer mixcomprising:

a. separate granular triboelectrically chargeable carrier particles, and

b. a developer powder comprising:

1. a coloring agent selected from the group consisting of dyes andpigments,

2. a resin blend having a triboelectric relationship of oppositepolarity with respect to said carrier particles and having a sharpmelting point within the range of about 70 C. to about 165 C., saidresin blend being formed by mixing the resin components in their moltenstate and being composed of:

i. an infrangible thermoplastic polyamide resin formed by reacting ahigh molecular weight polyene fatty acid or ester thereof with an amine,said polyamide resin having a fracturing value of at least 1,000 gramcentimeters, and

ii. a highly frangible thermoplastic resin having a fracturing value notgreater than 200 gram centimeters, said fracturing values being measuredby the falling ball method on a wafer of resin maintained at 100 F. and3.75 cm. in diameter and 0.5 cm. in thickness, whereby developed imagesof substantially improved density can be formed over extended operatingperiods.

4. The method of making an electrostatic copy on an electrostaticrecording member comprising the steps of:

electrostatically charging said member in the dark;

exposing the charged member to a pattern of light and shadow to producethereon an electrostatic charge image;

developing said charge image by applying thereon a developer mix, saiddeveloper mix comprising:

a. separate granular triboelectrically chargeable carrier particles,

b. a developer powder comprising:

1. a coloring agent selected from the group consisting of dyes andpigments, and

2. a resin blend having a triboelectric relationship of oppositepolarity with respect to said carrier particles and having a sharpmelting point within the range of about 70 C. to about 165 C., saidresin blend being formed by mixing the resin components in their moltenstate and being comprised of:

i. a major portion of an infrangible thermoplastic polyamide resinformed by reacting a high molecular weight polyene fatty acid or estersthereof with an amine, and

ii. a minor portion ofa highly frangible thermoplastic resin having afracturing value not greater than 200 gram cm., the frangibility of theresins being measured by the falling ball method on a wafer of resinmaintained at 100 F. and 3.75 cm. in diameter and 0.5 cm. in thickness,whereby developed images of substantially improved density can be formedover extended operating periods.

5. The method as claimed in claim 4 wherein the frangible resin is amaleic anhydride rosin-modified rosin.

6. The method of making an electrostatic copy on an electrostaticrecording member comprising the steps of:

electrostatically charging said member in the dark;

exposing the charged member to a pattern of light and shadow to producethereon an electrostatic charge image;

developing said charge image by applying thereon an electroscopic powdersuitable for developing said electrostatic charge images, said powderconsisting essentially of:

i. frangible and infrangible thermoplastic resins combined when in theirmolten state to form a miscible mixture, said mixture having physicalproperties which are distinct from either of the components comprisingsaid mixture, a softening point not less than 130 F., and a meltingpoint below the char point of paper to which it is applied and changingfrom discrete particles to a flowable state within 8 of said meltingpoint, said frangible resin constituting in the range of from 10 percentto 91 percent by weight of the electroscopic powder and having afracturing value not greater than 200 gram cms.,

ii. said infrangible resin being a polyamide resin formed by reacting ahigh molecular weight polyene fatty acid or esters thereof with an amineand constituting in the range of from 9 percent to percent by weight ofthe electroscopic powder and having a fracturing value of at least 1000gram centimeters, the fracturing value of the resin being measured at F.by the falling ball method on a wafer of a resin 3.75 cm. in diameterand 0.5 cm. in thickness.

7. The method of making an electrostatic copy as claimed in claim 6wherein said electroscopic powder has a melting point in the range offrom 250 to 235 F.

8. The method of making an electrostatic copy as claimed in claim 7wherein said electroscopic powder is constituted of from 10 percent to50 percent by weight of said polyamide resin and 50 percent to 90percent by weight of a maleic anhydride rosin-modified resin.

9. The method of making an electrostatic copy as claimed in claim 6wherein said electroscopic powder is comprised of from 30 percent to 40percent by weight of a polyamide resin, 40 percent to 50 percent byweight of a maleic anhydride rosin-modified resin and from 1 percent topercent by weight of a polyhydric alcohol tluxing agent.

10. The method of making an electrostatic copy as claimed in claim 6wherein said electroscopic powder is comprised of from 50 percent to 90percent by weight of said thermoplastic infrangible polyamide resin andfrom 5 percent to 40 percent by weight of a frangible thermoplasticresin component selected from the group consisting of maleic anhydriderosinmodified resin, esterified diphenolic resin, and phenolformaldehyderesins.

11. The method of making an electrostatic copy on an electrostaticrecording member comprising the steps of:

electrostatically charging said member in the dark;

exposing the charged member to a pattern of light and shadow to producethereon on electrostatic charge image;

developing said charge image by applying thereon a developer mixcomprising a granular electroscopic powder of colored thermoplasticparticles mixed with larger carrier particles, said thermoplasticparticles and said carrier particles having charges of oppositepolarity, said thermoplastic particles having as one component at leat9% by weight of a polyamide resin formed by reacting a high molecularweight polyene fatty acid or esters thereof with an amine heat-blendedwith a second frangible resin component to form a compositeelectroscopic powder having a fracturing value of at least 400 gramcms., said polyamide resin having a fracturing value of at least 1000gram cms.. the blend having a melting point in the range of about 158 F.to about 329 F.. and

fixing the developed electrostatic image by exposing the recordingmember to heat.

12. The method of making an electrostatic copy as claimed in claim 11wherein said polyamide resin is present in an amount of 50 percent to 90percent by weight of said electroscopic powder.

13. The method of making an electrostatic copy as claimed in claim 11wherein the second frangible resin component is amaleic-anhydride-polyhydric alcohol rosin-modified resin and is presentin an amount of from 9 percent to 50 percent by weight of saidelectroscopic powder.

14. The method of making an electrostatic copy as claimed in claim 11wherein the polyamide resin is a reaction product of polymerizedlinoleic acid and ethylenediamine.

15. The method of making an electrostatic copy as claimed in claim 11wherein the electroscopic powder has an average particle size in therange of from four microns to ten microns.

16. The method of making an electrostatic copy on an electrostaticrecording member comprising the steps of:

clectrostatically charging said member in the dark;

exposing the charged member to a pattern of light and shadow to producethereon an electrostatic charge image; developing said charge image byapplying thereon a developer mix comprising: A. separate granulartriboelectrically chargeable carrier particles, and B. a developerpowder comprising:

i. a coloring agent selected from the group consisting of dyes andpigments, ii. a resin blend having a triboelectric relationship ofopposite polarity with respect to said carrier particles, a meltingpoint in the range of about 158 F. to about 329 F. wherein the blendchanges from discrete particles to a flowable state within 8 F. of saidmelt point. said resin blend being formed by mixing the resin componentsin the molten state and being composed of a. at least 9% by weight ofsaid powder of an infrangible thermoplastic polyamid resin formed byreacting a high molecular weight polyene fatty acid or ester thereofwith an amine, said polyamide resin having a fracturing value of atleast 1000 gram centimeters,

b. a highly frangible thermoplastic resin having a fracturing value notgreater than 200 gram centimeters,

said blend having a fracturing value of at least 400 gram centimeters, aparticle size in the range of l to 74 microns, and a softening point ofabout 130 F., said fracturing values being measured by the falling ballmethod on a wafer of resin maintained at F. and 3.75 centimeters indiameter and 0.5 centimeters in thickness,

whereby developed images of substantially improved density can be formedover extended operating periods.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENTNO. 3,901,695 DATED August 26, 1975 INVENT 1 Loren E. Shelffo Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 4, line 45, "50 should read --5 column 6, line 22, "resins"should read ---rosins--; column 7, line 13, resin-modified" should read--rosin-modiied--; column 7, lines 36 and 37, "EZ-8-58T" should read--EZ8-58T--; column 7, line 39, afteg "15" there should be inserted--parts--; column 11, line '7, "150 F" should read --158 F-.

Signed and Scaled this second Day of W191i [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DAMN Arresting Officer Commissioner oj'Parenrsand Trademarks

1. THE METHOD OF MAKING AN ELECTROSTATIC COPY ON AN ELECTROSTATICRECORDING MEMBER COMPRISING THE STEPS OF ELECTROSTATICALLY CHARGING SAIDMEMBER IN THE DARK, EXPOSING THE CHARGED MEMBER TO A LIGHT PATTERN TOPRODUCE THEREON AN ELECTROSTATIC CHARGE IMAGE, DEVELOPING SAID CHARGEIMAGE BY APPLYING THEREON AN ELECTROSCOPIC POWDER, SAID ELECTROSCOPICPOWDER COMPRISING A BLEND OF INFRANGIBLE, SHARP-MELTING, THERMOPLASTICPOLYAMIDE RESINS AND A SHARP-MELTING HIGHLY FRANGIBLE, THERMOPLASTICRESIN, SAID BLEND BEING ACCOMPLISHED BY MELTING THE RESIN COMPONENTSTOGETHER TO FORM A MISCIBLE MIXTURE, SAID INFRANGIBLE RESIN COMPONENTHAVING A FRACTURING VALUE OF AT LEAST 1000 GRAM CENTIMETERS WHENMEASURED BY THE FALLING BALL METHOD AT 100*F. ON A WAFER OF RESIN 3.75CENTIMETERS IN DIAMETER AND 0.5 CENTIMETERS IN THICKNESS, A MELTINGRANGE NOT GREATER THAN 8*F. BEING PRESENT IN AN AMOUNT RANGING FROM 9 TO90% BY WEIGHT OF SAID GRANULAR POWDER, SAID HIGHLY FRANGIBLE RESINHAVING A FRACTURING VALUE NOT GREATER THAN 200 GRAM CENTIMETERS WHENMEASURED BY SAID FALLING BALL METHOD AND A MELTING RANGE NOT GREATERTHAN 8*F. AND THEREAFTER FIXING SAID DEVELOPED CHARGE IMAGE TO FORM APERMANENT IMAGE ON SAID RECORDING MEMBER.
 2. The method of making anelectrostatic copy on an electrostatic recording member comprising thesteps of: electrostatically charging said member in the dark; exposingthe charged member to a pattern of light and shadow to produce thereonan electrostatic charge image; developing said charge image by applyingthereon an electroscopic powder comprising a resin blend of: i. at least9% by weight of said powder of an infrangible thermoplastic polyamideresin formed by reacting a high molecular weight polyene fatty acid orester thereof with an amine, said polyamide resin having a fracturingvalue of at least 1,000 gram centimeters, and ii. a highly frangiblethermoplastic resin having a fracturing value not greater than 200 gramcentimeters, said resin blend being formed by mixing the resincomponents in their molten state and said blend further having a sharpmelting point within the range of about 150* F. to about 329* F., saidfracturing values being measured by the falling ball method on a waferof resin maintained at about 100* F. and 3.75 cm. in diameter and 0.5cm. in thickness.
 2. a resin blend having a triboelectric relationshipof opposite polarity with respect to said carrier particles and having asharp melting point within the range of about 70* C. to about 165* C.,said resin blend being formed by mixing the resin components in theirmolten state and being composed of: i. an infrangible thermoplasticpolyamide resin formed by reacting a high molecular weight polyene fattyacid or ester thereof with an amine, said polyamide resin having afracturing value of at least 1,000 gram centimeters, and ii. a highlyfrangible thermoplastic resin having a fracturing value not greater than200 gram centimeters, said fracturing values being measured by thefalling ball method on a wafer of resin maintained at 100* F. and 3.75cm. in diameter and 0.5 cm. in thickness, whereby developed images ofsubstantially improved density can be formed over extended operAtingperiods.
 2. a resin blend having a triboelectric relationship ofopposite polarity with respect to said carrier particles and having asharp melting point within the range of about 70* C. to about 165* C.,said resin blend being formed by mixing the resin components in theirmolten state and being comprised of: i. a major portion of aninfrangible thermoplastic polyamide resin formed by reacting a highmolecular weight polyene fatty acid or esters thereof with an amine, andii. a minor portion of a highly frangible thermoplastic resin having afracturing value not greater than 200 gram cm., the frangibility of theresins being measured by the falling ball method on a wafer of resinmaintained at 100* F. and 3.75 cm. in diameter and 0.5 cm. in thickness,whereby developed images of substantially improved density can be formedover extended operating periods.
 3. The method of making anelectrostatic copy on an electrostatic recording member comprising thesteps of: electrostatically charging said member in the dark; exposingthe charged member to a pattern of light and shadow to produce thereonan electrostatic charge image; developing said charge image by applyingthereon a developer mix comprising: a. separate granulartriboelectrically chargeable carrier particles, and b. a developerpowder comprising:
 4. The method of making an electrostatic copy on anelectrostatic recording member comprising the steps of:electrostatically charging said member in the dark; exposing the chargedmember to a pattern of light and shadow to produce thereon anelectrostatic charge image; developing said charge image by applyingthereon a developer mix, said developer mix comprising: a. separategranular triboelectrically chargeable carrier particles, b. a developerpowder comprising:
 5. The method as claimed in claim 4 wherein thefrangible resin is a maleic anhydride rosin-modified rosin.
 6. Themethod of making an electrostatic copy on an electrostatic recordingmember comprising the steps of: electrostatically charging said memberin the dark; exposing the charged member to a pattern of light andshadow to produce thereon an electrostatic charge image; developing saidcharge image by applying thereon an electroscopic powder suitable fordeveloping said electrostatic charge images, said powder consistingessentially of: i. frangible and infrangible thermoplastic resinscombined when in their molten state to form a miscible mixture, saidmixture having physical properties which are distinct from either of thecomponents comprising said mixture, a softening point not less than 130*F., and a melting point below the char point of paper to which it isapplied and changing from discrete particles to a flowable state within8* of said melting point, said frangible resin constituting in the rangeof from 10 percent to 91 percent by weight of the electroscopic powderand having a fracturing value not greater than 200 gram cms., ii. saidinfrangible resin being a polyamide resin formed by reacting a highmolecular weight polyene fatty acid or esters thereof with an amine andconstituting in the range of from 9 percent to 90 percent by weight ofthe electroscopic powder and having a fracturing value of at least 1000gram centimeters, the fracturing value of the resin being measured at100* F. by the falling ball method on a wafer of a resin 3.75 cm. indiameter and 0.5 cm. in thickness.
 7. The method of making anelectrostatic copy as claimed in claim 6 wherein said electroscopicpowder has a melting point in the range of from 250* to 235* F.
 8. Themethod of making an electrostatic copy as claimed in claim 7 whereinsaid electroscopic powder is constituted of from 10 percent to 50percent by weight of said polyamide resin and 50 percent to 90 percentby weight of a maleic anhydride rosin-modified resin.
 9. The method ofmaking an electrostatic copy as claimed in claim 6 wherein saidelectroscopic powder is comprised of from 30 percent to 40 percent byweight of a polyamide resin, 40 percent to 50 percent by weight of amaleic anhydride rosin-modified resiN and from 1 percent to 10 percentby weight of a polyhydric alcohol fluxing agent.
 10. The method ofmaking an electrostatic copy as claimed in claim 6 wherein saidelectroscopic powder is comprised of from 50 percent to 90 percent byweight of said thermoplastic infrangible polyamide resin and from 5percent to 40 percent by weight of a frangible thermoplastic resincomponent selected from the group consisting of maleic anhydriderosin-modified resin, esterified diphenolic resin, andphenolformaldehyde resins.
 11. The method of making an electrostaticcopy on an electrostatic recording member comprising the steps of:electrostatically charging said member in the dark; exposing the chargedmember to a pattern of light and shadow to produce thereon onelectrostatic charge image; developing said charge image by applyingthereon a developer mix comprising a granular electroscopic powder ofcolored thermoplastic particles mixed with larger carrier particles,said thermoplastic particles and said carrier particles having chargesof opposite polarity, said thermoplastic particles having as onecomponent at leat 9% by weight of a polyamide resin formed by reacting ahigh molecular weight polyene fatty acid or esters thereof with an amineheat-blended with a second frangible resin component to form a compositeelectroscopic powder having a fracturing value of at least 400 gramcms., said polyamide resin having a fracturing value of at least 1000gram cms., the blend having a melting point in the range of about 158*F. to about 329* F., and fixing the developed electrostatic image byexposing the recording member to heat.
 12. The method of making anelectrostatic copy as claimed in claim 11 wherein said polyamide resinis present in an amount of 50 percent to 90 percent by weight of saidelectroscopic powder.
 13. The method of making an electrostatic copy asclaimed in claim 11 wherein the second frangible resin component is amaleic-anhydride-polyhydric alcohol rosin-modified resin and is presentin an amount of from 9 percent to 50 percent by weight of saidelectroscopic powder.
 14. The method of making an electrostatic copy asclaimed in claim 11 wherein the polyamide resin is a reaction product ofpolymerized linoleic acid and ethylenediamine.
 15. The method of makingan electrostatic copy as claimed in claim 11 wherein the electroscopicpowder has an average particle size in the range of from four microns toten microns.
 16. The method of making an electrostatic copy on anelectrostatic recording member comprising the steps of:electrostatically charging said member in the dark; exposing the chargedmember to a pattern of light and shadow to produce thereon anelectrostatic charge image; developing said charge image by applyingthereon a developer mix comprising: A. separate granulartriboelectrically chargeable carrier particles, and B. a developerpowder comprising: i. a coloring agent selected from the groupconsisting of dyes and pigments, ii. a resin blend having atriboelectric relationship of opposite polarity with respect to saidcarrier particles, a melting point in the range of about 158* F. toabout 329* F. wherein the blend changes from discrete particles to aflowable state within 8* F. of said melt point, said resin blend beingformed by mixing the resin components in the molten state and beingcomposed of a. at least 9% by weight of said powder of an infrangiblethermoplastic polyamid resin formed by reacting a high molecular weightpolyene fatty acid or ester thereof with an amine, said polyamide resinhaving a fracturing value of at least 1000 gram centimeters, b. a highlyfrangible thermoplastic resin having a fracturing value not greater than200 gram centimeters, said blend having a fracturing value of at least400 gram centimeters, a particle size in the range of 1 to 74 microns,and a softening point of about 130* F., said fracturing values beingmeasured by the falling ball method on a wafer of resin maintained at100* F. and 3.75 centimeters in diameter and 0.5 centimeters inthickness, whereby developed images of substantially improved densitycan be formed over extended operating periods.